Treatment of light petroleum distillates



July 30, 1935. I R. E. BURK 2,009,954

I TREATMENT 0F LIGHT PETROLEUM DISTILLATES n l Filed Sept. 2, 1933 ATTORNEYJ;

'Patented July 30, 1935 UNITED :STATES TREATMENT. 0F LIGHT PETROLEUM DIsTlILATEs Robert enurk, cleveland, ohio, assignbf' to The Y Standard Oil Company, Cleveland, Ohio, a c'orporation of 0hio Application september z, 193s, serial No. 688,015

f s claims. c1. 19e-32) This invention relates to the treatment of light petroleum distillates, and more particularly the purifying of such distillates containing sulphur; and it is'among the objects of the invention to 5 provide a process which is highly desirable in action, and which allows of 'convenient control, and economy of materials. Other objects and advantages will appear as the description proceeds.

l0 To the accomplishment of the foregoing and vrelated ends, the invention, then, comprises the features hereinafter fully described, and particlarly pointed out in the claims, the following descrlption and the annexed drawing setting forth i5 in detail-an illustrativembodiment of the in- 'ventina' this. being indicative however, of but i e of the various ways in which the principle of invention may be employed.

aid annexed drawing:-

sole figure is a schematic illustration on er of a flow sheet, showing an embodimeer j the invention'.

The light petroleum distillate, such as gasoline, kerosene, etc., containingsulphur, as in the form gs/of mercaptans, is 'subjected to the action of aqueous sodium`hydroxide solution. Mercaptans are. converted into sodium. mercaptides thereby. Desirably', the distillate is brought into contact with the sodium hydroxide solution in counter- 3o 'current ilow\ arrangement, as for instance a series Vmercaptan-impurities 'in'v the f distillate being treated,'becomes' loaded up with sodium mercaptides, butin accordance with the present process,- this is obviated' and the treating solution is main-- 45 tained suiiiciently free from mercaptide secunialation to operate in continuous manner the Aon-coming distillate. For this purpose, in a suitable-point of the. cycle,the` aqueous soda solution` carrying the mercaptides picked up iron the 5o treatment of the distillate, is washed with a solution of sulphur caniod by a suitable solvent, such that the sulphur solution canV be adequately separated from the aqueous sodium hydroxide solution. As convenient solvents for the sulphur, or-

55 ganic liquids such as benzol, petroleum distillates, particularly naphtha, may be employed, 'and the sulphursolution therein maybe substantially a saturated solution. Inthevtreatment of the mercaptan-containing petroleum distillate with the sodium hydroxide solution, thev general .type of reaction occurring may be illustrated by the .equation NaOH+HSR=NaSR+HzQ The NaSR is ofcourse formed in minor proportion, such as to constitute an accumulating impurity in the NaOH solution. When the NaOH solution thus containing mercaptide is subjected to the action of the solution of sulphur, the mer. captide content of the sodium hydroxide solution is changed into compounds on the order of disulphides, as illustrated generally by the equation 2NaSR+S=RS-SR+Naz$-. although other complicating reactions also occur. With a suitable organic solvent as the carrier for the sulphur, Ya double function may be realized at this point, in that thesulphur may be carried out by the same solvent, A cleaningr ,or regenerating of the sodium hydroxide solution may thus be carried Y the concentration of the sodium hydroxide socycledto treat the petroleum distillate however contains enough free sulphur from the polysul- Even if an excess of free sulphur should be lthus presented to the distillate being finished, it would do no harm, if the distillate is not so cracked as to go unstable in gum and color.

The sodium hydroxide solution-ir y be of desired or convenient strength, for instance somewherein the lneighborhood of .'iper' cent.

As an example: A mercaptan-containing gasoline is washed with an aqueous solution of sodium hydroxide of about seven per cent, the gasphides to sweeten the distillate being iinshed.`

oline and the alkali solution being passed coun- 'ter-currently to each other through suitable chambers 2, 3, l, allowing adequate mixing and then layer-separation and oi-ilow in succession, the washed gasoline being taken off from the last of the series, while the caustic solution is taken oil from the iirst of the series, and is then brought into thorough admixture ina suitable chamber 5 with about an equal' volume of a nearly saturated solution or sulphur in petroleum naphtha. The liquid mixture is then passed on to a settling chamber 6 where the naphtha-sul-l phur solution is drawn of! and recycled back to the mixing chamber, while the aqueous solution 'of sodium hydroxide is passed on and recycled to the series of gasoline-keating chambers, 4, 3, 2, an intermediate filtration or settling or coolin'g being carried out if desired.

It is thus seen that sulphur compounds, such as mercaptans, may be removed from gasoline and the like, in a highly advantageous manner, while the caustic soda solution so employed may be progressively kept clear of undesired mercaptlde accumulation' by treatment also operable on a cycling basis. l

Other modesof applying the principle of the invention may be employed, change being made as lregards the details described, provided the features stated in any of the following claims, o1 the equivalent of such, be employed.

I therefore particularly point out and distinctly claim as my invention:-l

1. A process of purifying light petroleum distillates, which comprises mixing the distillate with an aqueous solution of sodium hydroxide, separating the distillate from the sodium hydroxide solution, mixing said separated sodium hydroxide solution with a hydrocarbon solution of sulphur in the absence of the distillate, separating the sodium hydroxide solution and the sulphur solution, and mixing the separated sodium hydroxide solution with petroleum distillate.

2. A process of purifying light petroleum distillates, which comprises mixing the distillate with an aqueous solution oi sodium hydroxide in counter-current ilow, separating the distillate from'the sodium hydroxide solution, mixing said separated sodium hydroxide solution with a hydrocarbon solution of sulphur in the absence of the distillate, l separating the 'sodium hydroxide solution and the sulphur solution, and flowing the sodium sydroxide solution back in counter-current mixing with petroleum distillate. l

3. A proces of purifying light petroleum distillates, which comprises mixing the distillate with a 1 per cent aqueous solution of sodium hydroxide in counter-current flow, separating the distillate from the sodium hydroxide solution, mixing said separated sodium hydroxide solution with a hydrocarbon solution of sulphur in the absence of the distillate, separating the sodium hydroxide solution and the sulphur solution, and flowing the sodium hydroxide solution back in counter-current mixing with petroleum distillate.

ROBERT E. BURK. 

